Finding Blank Columns in CSV

Mon Oct 5 16:56:52 EDT 2015

On 2015年10月05日 13:29:03 +0000, Jaydip Chakrabarty wrote:
> Hello,
>> I have a csv file like this.
>> Name,Surname,Age,Sex abc,def,,M ,ghi,,F jkl,mno,,
> pqr,,,F
>> I want to find out the blank columns, that is, fields where all the
> values are blank. Here is my python code.
>> fn = "tmp1.csv"
> fin = open(fn, 'rb')
> rdr = csv.DictReader(fin, delimiter=',')
> data = list(rdr)
> flds = rdr.fieldnames fin.close()
> mt = []
> flag = 0 for i in range(len(flds)):
> for row in data:
> if len(row[flds[i]]):
> flag = 0 break
> else:
> flag = 1
> if flag:
> mt.append(flds[i]) flag = 0
> print mt
>> I need to know if there is better way to code this.
>> Thanks.

Assuming all the records have the same number of fields:
I'd create a list of flags of length numfields, all set to 0
then for each record, I*d set flag[n] = 1 if field[n] has content
then I'd check if I still have any 0 flags, and if I do, process the next 
record
As soon as I have no 0 flags, I can stop processing records, as this 
means I have no empty columns.
It might be more efficient if, when checking a record, I only tested the 
fields for which flag was still 0.
Example (untested)
flags = [False for x in rdr.fieldnames]
for row in data:
 blanks = False
 for i in range(len(flags)):
 if not flags[i]:
 if len(row[i]) == 0:
 flags[i] = True
 else:
 blanks = True
 if not blanks:
 break
-- 
Denis McMahon, denismfmcmahon at gmail.com